1. Field of the Invention
This invention relates to electrical circuit makers and breakers of the liquid contact type with piston or plunger-like means having a unitary bridging contact function. There may be single-pole, double-throw or single-pole, single-throw embodiments. In the case of the single-pole, single-or-double-throw arrangement, the container may form at least one contact.
2. Description of the Prior Art
U.S. Pat. No. 3,240,900 of Halff et al shows a mercury switch with two aligned contact rods separated from each other by a small amount. Within the hollow chamber is located a pool of mercury and a magnetizable plunger normally floating in the pool. About the chamber is wound an actuating coil for generating a magnetic field which will drive the plunger down into the pool of mercury, thereby elevating the surface level of the mercury until it envelops the contact ends of the two rods to close the switch.
The Beausoleil et al publication entitled "Latch Relay" in the IBM Technical Disclosure Bulletin Vol. 11, No. 11, p. 1467 shows an elongated tube with a magnetically actuable switch with a colloidal suspension of an electroconductive liquid with magnetic particles in it which can be reciprocated at will under control of an external magnetic field.
Hurvitz U.S. Pat. No. 3,289,126 shows a mercury switch with a suspension of carbonyl iron particles in it and with cylindrical contact cups at opposite ends. An external magnetic field causes the mercury to bridge the magnetically and electrically inactive material between the cups.
U.S. Pat. No. 3,786,217 of Bitko shows an elongated armature slidable on a mercury film which forms electrical contacts with contacts located at the opposite ends of a cylindrical glass tube. It includes stop members to prevent collision of the contacts at the ends of the tube with the contacts on the ends of the armature, but close enough so that the gap between contacts in the closed position is bridged by mercury droplets on the confronting contacts.
It is believed that sticking of the armature in mercury switches which employ end wall contact is probably caused by insufficient spacing between the armature contact element in the end wall and the confronting stationary contact element. As a result of small spacing, growth of fibers of metal may occur. Such fibers may affix the armature to the contact.
Accordingly, it is an object of this invention to eliminate end wall contact in linear motion liquid contact switches.
Another object of this invention is to avoid close proximity between all solid metallic parts of a linear liquid contact switch.
In accordance with this invention, sticking is avoided by means of eliminating all close proximity of solid metallic parts and providing a stopping force with a magnet, pneumatic effect or a hydraulic effect which stops the armature well short of the end wall. Dimensions are selected so that sufficient clearance between the armature and the stationary contacts is maintained by relatively thick films of conducting liquid. The force for moving the armature is provided by magnetic or other linear force producing means.
In one aspect of this invention, a linear motion liquid contact switch includes an armature which slides concentrically with respect to a pair of axial contacts which are in the form of cylindrical rods.
In an alternative arrangement, an armature rod slides within two spaced contact cylinders of larger diameter than the rod.